update link to unit tests (thanks, @Bijaelo)

Author: eddelbuettel

ChangeLog

@@ -1,3 +1,7 @@
+2021-02-23  Dirk Eddelbuettel  <edd@debian.org>
+
+	* Contributing.md: Update unit test link to tinytest
+
 2021-02-08  Dirk Eddelbuettel  <edd@debian.org>
 
 	* DESCRIPTION (Author): Add Inaki to the team

Contributing.md

@@ -30,7 +30,7 @@ post an issue outlining some motivation for your pull request to ensure that
 some discussion around the appropriate resolution for the issue occurs first.
 
 We would prefer it if your PR also included
-[unit tests](https://github.com/RcppCore/Rcpp/tree/master/inst/unitTests). Additions
+[unit tests](https://github.com/RcppCore/Rcpp/tree/master/inst/tinytest). Additions
 to the [ChangeLog](https://github.com/RcppCore/Rcpp/blob/master/ChangeLog) and
 [NEWS](https://github.com/RcppCore/Rcpp/blob/master/inst/NEWS.Rd) are also
 appreciated.